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基于钨钼的电化学性质差异,以铜为还原剂,在添加EDTA络合剂和无络合剂作用的条件下,研究了EDTA用量、pH值、还原时间、反应温度对钼还原率的影响。结果表明,添加EDTA络合剂不利于钼还原率的提高;反应可采用铜直接还原,选择pH=1.0~1.5、反应温度60℃及延长还原时间,利于钼还原率的提高。 相似文献
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将经典的高氯酸脱水重量法测定硅改为以碱性熔剂过氧化钠,在高温条件下熔融酸化处理试样后定容,在C(H^+)=0.1~0.6mol/L酸度时,加入钼酸铵与正硅酸生成硅钼杂多酸(硅钼黄),用草酸配位铁使溶液透明并破坏磷、砷等元素与钼酸铵生成的杂多酸消除干扰。用硫酸亚铁铵还原硅钼黄为硅钼蓝,测量吸光度求得硅量。方法操作简便、快速,分析结果准确,缩短了分析周期,提高工效24倍。 相似文献
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本文研究了在酸性介质中,有铋盐存在下加入钼酸铵与磷生成铋磷钼杂多酸的显色反应。用盐酸羟胺掩蔽铁,抗坏血酸还原铋磷钼杂多酸为铋磷钼蓝,借此光度法测定磷。 相似文献
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钒钼共存时在约0.60mol/L的硫酸酸度下,以铜盐为催化剂,硫脲为还原剂,至少30mg钒不干扰钼与硫氰酸盐的显色反应。方法应用于五氧化二钒中钼量的测定。分析结果令人满意。 相似文献
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试样经过高温分解,用硫酸调整酸度后,加钼酸铵形成硅钼杂多酸,先用草酸破坏磷,砷化合物,用亚铁还原为钼兰,根据色泽的深浅,测定二氧化硅的含量。 相似文献
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Reduction of the antioxidant lipoic acid has been proposed to be catalyzed in vivo by lipoamide dehydrogenase (LipDH) or glutathione reductase (GR). We have found that thioredoxin reductase (TR) from calf thymus, calf liver, human placenta, and rat liver efficiently reduced both lipoic acid and lipoamide with Michaelis-Menten type kinetics in NADPH-dependent reactions. In contrast to LipDH, lipoic acid was reduced almost as efficiently as lipoamide. Under equivalent conditions at 20 degrees C, pH 8.0, mammalian TR reduced lipoic acid by NADPH 15 times more efficiently than the corresponding NADH dependent reduction catalyzed by LipDH (297 min-1 for TR vs. 20.3 min-1 for LipDH). Moreover, TR was 2.5 times faster in reducing lipoic acid with NADPH than in catalyzing the reverse reaction (oxidation of dihydrolipoic acid with NADP+). In contrast, LipDH was only 0.048 times as efficient in the forward reaction as compared to the reverse reaction (using NADH and NAD+). We conclude that all or part of the previously described NADPH-dependent lipoamide dehydrogenase (diaphorase) activities in mammalian systems should be attributed to TR. Our results suggest that in mammalian cells a significant part of the therapeutically important reduction of lipoic acid is catalyzed by thioredoxin reductase. 相似文献
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以某公司复杂碲铜物料为原料,采用双氧水氧化浸出-草酸沉铜-还原碲工艺回收复杂碲铜物料中的碲。研究了浸出温度、H2SO4浓度、双氧水的加入量、液固比、浸出时间对碲浸出效果的影响,草酸钠过量系数和反应温度对沉铜效果的影响以及亚硫酸钠用量对还原效果的影响。试验结果表明:在H2SO4浓度110 g·L-1、双氧水的加入量为理论量的1.2倍、液固比6∶1、浸出温度80~85℃、浸出时间4 h时,碲、铜浸出效果最好;在草酸钠为理论量的1.2倍、反应温度65~75℃时,沉铜效果最好;在亚硫酸钠用量为理论量的1.6倍时还原沉碲的效果最好。碲以碲粉的形式回收,铜以草酸铜的形式回收,碲、铜的回收率分别为98.5%和98%。 相似文献
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The report describes a method of deproteinizing serum that combines the action of acids with microwave irradiation. The acid concentration is ten times smaller than in the usual acid deproteinization method and the results are similar. The main advantages of the proposed method are the maintenance of the pH of the supernatant at around 5, and the reduction of the concentration of the deproteinizing agent. The procedure was applied to the determination of ethylenethiourea in serum samples by HPLC with spectrophotometric detection. Using 0.5 ml of serum, 0.04 microgram of ethylenethiourea were determined with recoveries between 89 and 109%. 相似文献
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Bioleaching of copper from the flue dust of the Sarcheshmeh copper smelter has been investigated. A series of continuous tests were carried out in two-stages of airlift bioreactors inoculated with the acidophilic, iron and sulfur oxidizing bacteria, initially derived from acid mine drainage. The effects of different parameters such as pulp density, retention time and temperature on the mesophile bioleach performance of the copper sulfide rich dust were evaluated after pre-leaching with dilute acid. Pulp densities of 2% and 4% gave the same oxidation–reduction potential in both reactors. However, increasing the average pulp density to 7% generated an unstable oxidation–reduction potential in the first bioreactor at 34 °C. Overall copper extractions calculated for 2%, 4% and 7% pulp densities were 90%, 89% and 86% with mean retention times of 2.7, 4 and 5 days, respectively. The process is net acid consuming and has the potential for further development and feasibility studies. 相似文献
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K Matsushita T Yakushi H Toyama O Adachi H Miyoshi E Tagami K Sakamoto 《Canadian Metallurgical Quarterly》1999,1409(3):154-164
Alcohol dehydrogenase (ADH) of acetic acid bacteria functions as the primary dehydrogenase of the ethanol oxidase respiratory chain, where it donates electrons to ubiquinone. In addition to the reduction of ubiquinone, ADHs of Gluconobacter suboxydans and Acetobacter aceti were shown to have a novel function in the oxidation of ubiquinol. The oxidation activity of ubiquinol was detected as an ubiquinol:ferricyanide oxidoreductase activity, which can be monitored by selected wavelength pairs at 273 and 298 nm with a dual-wavelength spectrophotometer. The ubiquinol oxidation activity of G. suboxydans ADH was shown to be two times higher in 'inactive ADH', whose ubiquinone reductase activity is 10 times lower, than with normal 'active' ADH. No activity could be detected in the isolated subunit II or subunit I/III complex, but activity was detectable in the reconstituted ADH complex. Inactive and active ADHs exhibited a 2-3-fold difference in their affinity to ubiquinol despite having the same affinity to ubiquinone. Furthermore, the ubiquinol oxidation site in ADH could be distinguished from the ubiquinone reduction site by differences in their sensitivity to ubiquinone-related inhibitors and by their substrate specificity with several ubiquinone analogues. Thus, the results strongly suggest that the reactions occur at different sites. Furthermore, in situ reconstitution experiments showed that ADH is able to accept electrons from ubiquinol present in Escherichia coli membranes, suggesting the ubiquinol oxidation activity of ADH has a physiological function. Thus, ADH of acetic acid bacteria, which has ubiquinone reduction activity, was shown to have a novel ubiquinol oxidation activity, of which the physiological function in the respiratory chain of the organism is also discussed. 相似文献
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研究了刚果(金)某铜钴矿的硫酸还原浸出。结果表明,在矿样粒度为-0.074mm占90%、终点pH为1.5、SO2用量为理论量的1.5倍(4kg/t)、浸出温度80℃、浸出时间120min、液固比4∶1的条件下,铜、钴浸出率分别达到了93.35%和90.13%。在此基础上进行了模拟堆浸的柱浸试验,柱浸采用先浸铜再还原浸钴的分步浸出方式,铜浸出率达72%,钴浸出率为66%。 相似文献
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LG Lee SL Spurgeon CR Heiner SC Benson BB Rosenblum SM Menchen RJ Graham A Constantinescu KG Upadhya JM Cassel 《Canadian Metallurgical Quarterly》1997,25(14):2816-2822
We have synthesized a set of four energy transfer dyes and demonstrated their use in automated DNA sequencing. The donor dyes are the 5- or 6-carboxy isomers of 4'-aminomethylfluorescein and the acceptor dyes are a novel set of four 4,7-dichloro-substituted rhodamine dyes which have narrower emission spectra than the standard, unsubstituted rhodamines. A rigid amino acid linker, 4-aminomethylbenzoic acid, was used to separate the dyes. The brightness of each dye in an automated sequencing instrument equipped with a dual line argon ion laser (488 and 514 nm excitation) was 2-2.5 times greater than the standard dye-primers with a 2 times reduction in multicomponent noise. The overall improvement in signal-to-noise was 4- to 5-fold. The utility of the new dye set was demonstrated by sequencing of a BAC DNA with an 80 kb insert. Measurement of the extinction coefficients and the relative quantum yields of the dichlororhodamine components of the energy transfer dyes showed their values were reduced by 20-25% compared with the dichlororhodamine dyes alone. 相似文献
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Juan Bussi Mauricio Ohanian Milton Vázquez Enrique A. Dalchiele 《Canadian Metallurgical Quarterly》2002,128(8):733-739
The removal of mercury from hazardous wastes of a chlor-alkali plant was investigated by a combined process of acid attack and photoreduction treatment. The solution obtained by acid attack of the solid wastes was treated with ultraviolet irradiation in the presence of titanium dioxide and an organic agent (citric acid), leading to the selective precipitation of reduced mercury, while the other metal compounds remained in the solution. In spite of the large excess of non-reducible metal ions (100 times or more on a molar basis), more than 99% of the mercury initially present in the solid wastes was removed. Competitive adsorption of the different metal compounds on the titanium dioxide surface led to lower rates of mercury reduction. This combined process can be an efficient alternative method for mercury separation because the final effluents have reached a quality close to that of the standards imposed by international environmental agencies. 相似文献
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We recently reported that morphine inhibits growth of various human cancer cell lines (IC50/2.7-8.8 mM). We then extended the study using newly synthesized morphine derivatives, such as KT-90 and KT-87, which are analgesics 5 times more potent than morphine. KT-90 was found to inhibit growth of human cancer cell lines (IC50/42-70 microM) up to 80 times more potently than morphine. As for mechanisms of action, KT-90 and morphine induced apoptosis, and inhibited tumor necrosis factor alpha (TNF-alpha) gene expression induced by tumor promoters, okadaic acid and 12-O-tetradecanoylphorbol-13-acetate, associated with reduction of NF-kappaB DNA binding activity. This paper provides evidence that KT compounds confirmed the presence of anticancer activity of morphine in addition to its analgesic action. 相似文献